Long Term Evolution (LTE) system supports two duplexing modes, that is, Frequency Division Duplexing (FDD) and TDD. FIG. 1 is a schematic diagram illustrating a frame structure in a TDD system. Length of each radio frame is 10 ms, which is divided into two half-frames. Length of each half-frame is 5 ms. Each half-frame includes 8 time slots and 3 special domains. Length of each time slot is 0.5 ms. The 3 special domains refer to Downlink Pilot Time Slot (DwPTS), Guard Period (GP) and Uplink Pilot Time Slot (UpPTS). Sum of length of each special domain is 1 ms. Each subframe consists of two consecutive time slots, that is, Kth subframe includes time slots 2k and (2k+1). TDD system supports 7 kinds of UL-DL configurations, which are shown in Table 1. In Table 1, D represents a downlink subframe. U represents an uplink subframe. S represents a special subframe which includes 3 special domains mentioned above.
TABLE 1Config-Period ofurationswitchingsubframe numberindexpoint012345678905msDSUUUDSUUU15msDSUUDDSUUD25msDSUDDDSUDD310msDSUUUDDDDD410msDSUUDDDDDD510msDSUDDDDDDD610msDSUUUDSUUD
Based on Table 1, subframes 3, 4, 7, 8, and 9 are downlink subframes in some TDD UL-DL configurations. Meanwhile, subframes 3, 4, 7, 8 and 9 are uplink subframes in TDD UL-DL configurations. These subframes 3, 4, 7, 8 and 9 may be referred to as flexible subframes.
Theoretically, to adapt to service changes, a cell may employ TDD UL-DL configurations, which are different from that of an adjacent cell. Currently, changing TDD UL-DL configurations may be implemented with System Information Block type 1 (SIB1). However, changing delay of SIB1 is 640 milliseconds. SIB1 may only change 32 times every 3 hours at most, which may not better adapt to UL-DL service amount changes. To better adapt to the UL-DL service amount changes, when UL-DL service ratio doesn't match with a ratio of uplink subframe and downlink subframe in the TDD UL-DL configuration, the TDD UL-DL configuration may be adjusted timely.
One implementation method is as follows. Evolved Node B (eNB) may dynamically adjust the TDD UL-DL configurations, according to UL-DL service ratio changes. The eNB may also indicate direction of a flexible subframe, with scheduling information in a Physical Downlink Control Channel (PDCCH). User Equipment (UE) may determine whether a flexible subframe is an uplink subframe or a downlink subframe, by detecting the PDCCH, which is shown in FIG. 2. In FIG. 2, suppose the TDD UL-DL configuration indicated by SIB1 is TDD UL-DL configuration 2. Subframes 3, 4, 7, 8 and 9 are flexible subframes. That is, a corresponding flexible subframe may be determined as an uplink subframe or a downlink subframe, by detecting whether the PDCCH is uplink allocation authorization or a downlink allocation authorization. Suppose scheduling of uplink PUSCH and Hybrid Automatic Repeat Request (HARQ) comply with TDD UL-DL configuration 1. Thus, when detecting the uplink grant allocation authorization from subframe 1, subframe 7 is an uplink subframe. When detecting the downlink assignment allocation authorization from subframe 7, subframe 7 is a downlink subframe.
During the process of determining whether a flexible subframe is an uplink subframe or a downlink subframe, by using the uplink grant allocation authorization or the downlink assignment allocation authorization, the UE neither receive the uplink grant uplink allocation authorization from subframe 1, nor receive the downlink assignment downlink allocation authorization from subframe 7. Thus, the UE may not determine whether subframe 7 is an uplink subframe or a downlink subframe. However, the UE receives the downlink assignment downlink allocation authorization from subframe 6. And then, the UE doesn't learn whether subframe 6 is a special subframe or a normal common downlink subframe. Since when the eNB converts subframe 7 into an uplink subframe, subframe 6 should be a special subframe according to Table 1. When the eNB converts subframe 7 into a downlink subframe, subframe 6 should be a normal downlink subframe. However, since the UE neither receive the uplink grant from subframe 1, nor receive the downlink assignment from subframe 7, the UE cannot determine whether subframe 7 is an uplink subframe or a downlink subframe. Subsequently, the UE doesn't learn whether subframe 6 is a special subframe or a normal downlink subframe, as shown in FIG. 3.
When subframe 6 is a special subframe, subframe 6 includes three parts, which are respectively DwPTS, GP and UpPTS. Number of Orthogonal Frequency Division Multiplexing (OFDM) symbols used for the PDSCH transmission is obtained as follow. Subtract number of OFDM symbols used for control area transmission of PDCCH from 14 OFDM symbols to obtain an intermedia result, and then subtract OFDM symbol number of GP and UpPTS from the intermedia result. When subframe 6 is a normal downlink subframe, the OFDM symbol number in subframe 6 used for the PDSCH transmission is obtained as follows. Subtract number of OFDM symbols used for the control area transmission of the PDCCH from 14 OFDM symbols.
To enable the UE to explicitly learn number of OFDM symbols within subframe 6 used for PDSCH transmission, and enable the UE and eNB not to confuse the OFDM symbol number used for PDSCH transmission, the UE needs to be informed with a corresponding technical scheme, which is just the technical problem to be solved by the present disclosure currently.